Norway plans to be the first country in the world to become "carbon neutral" and cut its net greenhouse gas emissions to zero by 2050. The prime minister, Jens Stoltenberg, has proposed the move, expected to encourage other rich countries to act further and faster on climate change.

In a speech to the Labour party, Mr Stoltenberg said the greenhouse effect was the world's most dangerous environmental problem and that Norway had a responsibility to act urgently.

"By 2050 greenhouse gas emissions will have to be reduced drastically. Rich countries should become carbon neutral. This does not mean no emissions from the countries in question. But it does mean that each tonne of greenhouse gases emitted is to be offset by an equivalent reduction elsewhere. This adds up to zero emissions," he said.

"Norway will be at the forefront of international climate effort. I propose that in the period up to 2050 Norway will undertake to reduce global greenhouse gas emissions equivalent to 100% of our own emissions." He said the government would "sharpen" measures to meet its existing obligations under the Kyoto protocol by 10% in the period up to 2012, and had agreed to a 30% cut in emissions by 2030.

The prime minister's proposal propels Norway to the top of the international carbon cutting league. Britain has legally committed itself to cut greenhouse gas emissions by 60% up to 2050, California has proposed 80%, and both Sweden and Iceland have pledged where possible to stop all oil imports by then. Europe says it intends to cut emissions by 20% by 2020 and by 30% if others make similar cuts.

Like other wealthy countries, Norway intends to reach its target mainly by offsetting its 54m tonnes of carbon emissions a year using quotas bought on international markets. The country, which is the world's fifth largest oil exporter, has built up savings from oil and gas exports of nearly $300bn. Norwegian emissions per capita are about 11 tonnes, almost three times the world average.

Although the proposals were widely welcomed in Norway, critics argued that the country would be doing much more to fight climate change if it stopped producing oil and gas that other countries burn. "It should do more at home rather than use its vast oil wealth to buy its way out of the problem," said a spokesman for environmental group Greenpeace. "Norway should take responsibility for the 500m tonnes of emissions that it causes by its exports of oil and gas."

It was unclear last night whether Norway intended that its targets would include its large shipping and aviation emissions, which are not at the moment part of Kyoto treaty targets.

"Climate change is a question of solidarity and equity - two of the core values of social democracy," said Mr Stoltenberg. "Solidarity between generations and equity between rich and poor countries. We have fostered joint effort and a sense of community in our country with a view to creating equity."